CIE AS Chemistry (9701) exams from 2022

Revision Notes

3.6.2 Esters

Production of Esters

  • Esters are compounds with an -COOR functional group and are characterised by their sweet and fruity smells
  • They are prepared from the condensation reaction between a carboxylic acid and alcohol with concentrated H2SO4 as catalyst
    • This is also called esterification
  • The first part of the ester’s name comes from the alcohol and the second part of the name comes from the carboxylic acid
    • Propanol and ethanoic acid will give the ester propyl ethanoate


Carboxylic Acids & Derivatives Production of Esters, downloadable AS & A Level Chemistry revision notes

Esters are formed from the condensation reaction between carboxylic acids and alcohols

Hydrolysis of Esters

  • Esters can be hydrolysed to reform the carboxylic acid and alcohol by either dilute acid or dilute alkali and heat
  • When an ester is heated under reflux with dilute acid (eg. sulfuric acid) an equilibrium mixture is established as the reaction is reversible


Ester hydrolysis by dilute acid is a reversible reaction forming carboxylic acid and alcohol

  • However, when heated under reflux with dilute alkali (eg. sodium hydroxide) is an irreversible reaction and the ester is fully hydrolysed
  • This results in the formation of a sodium carboxylate salt which needs further acidification to turn into a carboxylic acid


Ester hydrolysis by dilute alkali is an irreversible reaction forming a sodium carboxylate salt and alcohol


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